Vehicle suspensions generally have various components, such as upper or lower control arms, that are fastened to support brakets by bushing joints. The typical bushing consists of inner and outer cylindrical metal sleeves with an intermediate rubber layer, with one end of the control arm, or some other suspension member, fixed to the outer sleeve. The typical support bracket consists of two spaced walls that are rigid to the vehicle frame or body with opposed circular openings in the walls small enough that the bushing inner sleeve cannot pass therethrough. The conventional bushing joint is formed by inserting the inner bushing sleeve between the bracket walls, aligned with the openings, and passing a threaded bolt therethrough. Then, a nut is tightened down against the outside of one of the bracket walls until the bolt head is drawn up tight against the outside of the other bracket wall. The inner bushing sleeve is thereby clamped between the inside surfaces of the walls to complete the joint. A drawback of such a joint is that the bushing inner sleeve is ideally made somewhat shorter than the nominal spacing between the bracket walls to assure easy insertion therebetween, and tolerance variations may in fact increase that differential. Therefore, as the clamping load is applied, the walls may tend to deform toward each other before the inside surfaces of the bracket walls are stopped by the ends of the bushing inner sleeve. the bracket walls must, therefore, be made thicker and stronger than they would otherwise have to be to absorb the clamping load deformation without weakening significantly. By the same token, the tolerance in the bushing sleeve-braket wall spacing differential has to be held more closely held than it otherwise would.
An attempt to solve some of the above problems may be seen in the German Offenlegungsschrift DE No. 33434250 A1. There, a pair of relatively thick, rigid spaced walls of a cast iron suspension component have a bushing sleeve clamped therebetween. One of the walls has an opening therethrough that, rather than being straight, tapers toward the opening in the other rigid wall. The bushing sleeve is deliberately made shorter than the spacing between the walls. A radially compressible split sleeve has a tapered outer surface that fits tightly within the tapered wall opening and a cylindrical inner surface that surrounds the bolt near the bolt head. The inside edge of the split sleeve is axially spaced from the end of the bushing sleeve before the nut is tightened down, so that the bolt head drage the split sleeve farther inside the tapered opening, radially compressing it untill it stops on the bushing sleeve. Further tightening of the nut draws the bolt head tight up against the split sleeve, instead of against the outside surface of the wall.
The joint so described above has drawbacks of its own, however, that make it inapplicable to the environment of spaced sheet metal walls. It must be assured that the surface of the tapered split sleeve will be radially tight against the surface of the tapered hole at whatever point that the split sleeve is stopped by the bushing sleeve, in order for the completed joint to be rattle free. To guarantee that, the split sleeve in its initial, uncompressed state must be larger than the tapered opening so as to be radially compressed continuously as it is pulled into the tapered hole. As a consequence, the surface of the tapered sleeve is dragged past the surface of the tapered wall opening continuously as the nut is tightened. This obviously creates a frictional force that would tend to deform the walls toward one another, a force that could be quite strong if the material of the tapered sleeve were resistant to compression. Such a force could easily deform relatively thinner, less rigid sheet metal bracket walls toward one another. Furthermore, the tapered sleeve could present a tolerance problem. The inner, cylindrical surface of the tapered sleeve closes up as the tapered sleeve is compressed. If the tapered sleever were to close on the bolt shaft before it had abutted the bushing sleeve, the tapered sleeve could not be compressed any further or move any farther into the tapered opening, and the joing could not be completed. Therefore, the inside diameter of the tapered sleeve would have to be held closely enough to assure that it did not close prematurely on the bolt shaft. In addition, the use of a tapered opening presupposes a relatively thick wall. The edge of an opening through a relatively thinner, sheet metal wall could not provide any significant taper. Tapered sleeves and tapered openings are more difficult to machine than straight, cylindrical sleeves and openings, as well.